Dodgy diesel-heads to the bridge please

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There have been lots of articles on the fact that a gadget has been installed that cheats exhaust emissions when detecting if the vehicle is on a rolling road.

So the questions are :-

how does it detect when it's on a rolling road?

how does it baffle the scientific instruments that have been used to detect ACTUAL levels of N0 and C02?

Reply to
Bertie Doe
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This has been answered a number of times recently.

It doesn't. It just retunes the engine to emit lower levels.

Reply to
Tim Streater

I don't know how VW did it, but if there is an accelerometer attached to the EMU, and the road wheels were belting along with no significant acceleration, you can be fairly certain you're on a treadmill.

But that's the point, in this condition the emissions are compliant.

Reply to
Graham.

a) It could spot trivial stuff like the steering's not being used, one set of wheels is not rotating (ABS sensors), a particular pattern of throttle applications and stuff like that. Who knows what they actually did, but it seems possible.

b) Fiddle with the fuelling and air to get a cleaner exhaust (for some definition of clean) at the expense of power or efficiency.

Reply to
Tim Watts

But the power output is not acceptable to the driver/marketplace if they were left like that.

Reply to
Bob Minchin

Who cares?

September car sales were at record levels. The VW Golf was the 4th best seller and the VW Polo was 5th.

Reply to
Michael Chare

Well you would not be steering much on a rolling road. As for baffling, the engine management can no doubt select a running mode with very low emissions once its been running for a while, but normal driving is dynamic and presumably cannot be tracked fast enough to stop it exceeding the no doubt daftly low amounts in the spec. This is my version of what a wheel in expert from one of the motoring organisations said in a phone in. Brian

Reply to
Brian-Gaff

Not at a;ll. ECU responds in milliseconds.

That's not the problem. The problem is that low NOx equates to a richer mixture, which screws the fuel consumption in cruise and at idle.

And its not the best for peak power either..

Reply to
The Natural Philosopher

When I first heard about the 'dodge' I assumed the EMU would be well aware of any load or, draw being put on it's pins?

Reply to
RayL12

Er, no, but what has that got to do with it anyway?

Reply to
The Natural Philosopher

I'm assuming that a machine is plugged into the EMU and that the EMU does the 'modifying'?

Reply to
RayL12

asumptions totally wrong

Carr is put on a rolling road and a sniffer shoved up its tailpipe

Reply to
The Natural Philosopher

It's nothing whatsoever to do with MOT emissions. It's all about type- approval tests in the US, where they don't even _HAVE_ a single national MOT.

NOx - the gas in question - isn't even measured in the MOT.

Reply to
Adrian

These are diesels: how do you define a rich or lean mixture for combustion occurring on the surface of many tiny droplets?

At any condition other than peak fuel demand, a diesel operates with considerable excess air, because the inlet air is not throttled.

Reply to
Kevin

By injecting more or less fuel, obviously.

That is not the point. And its not true of variable geometry turbo charged diesels either.

They operate with variable amounts of air.

And its not true across the whole combustion chamber either. Timing of injection pulse(s) makes a big difference, as does the swirl patterns of the airflow.

Essentially shoving fuel in at the point where peak temperature and pressure coincides with TDC gives the most power and econony at any given throttle setting, and the most NOx.

Reply to
The Natural Philosopher

You sure about that? Don't they need injection advance, the way petrol engines have ignition advance?

Andy

Reply to
Vir Campestris

Where did I say that injection time corresponds to peak pressure and temperature?

Reply to
The Natural Philosopher

Or indeed any injection at all.

This bit does give it away "shoving fuel in at the point where peak temperature and pressure coincides with TDC", does imply that if there is any "injection" that its at a point coinciding with TDC.

If that wasn't what you intended to say, where injection isn't the same as "shoving fuel in", then perhaps you can enlighten us?

Reply to
Fredxxx

Perhaps saying 'shoving fuel in at such a point so as to make peak pressure and temperature coincide with TDC...'

but its a lot of extra words

Reply to
The Natural Philosopher

But quite simply that isn't the case, as Andy was eluding to.

Fuel takes time to burn, it doesn't spontaneously explode when "shovelled in" or even "injected".

Therefore even diesel injection is carried out before TDC, in a similar way petrol engines have ignition advance.

Reply to
Fredxxx

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